Unilocular hepatic echinococcal cysts: Sonography and computed tomography findings

AIM: In endemic regions, unilocular hepatic echinococcal cysts (HEC) may be difficult to differentiate radiologically from simple non-parasitic cysts, especially if serological tests were negative. The aim of this descriptive study is to elucidate distinctive imaging findings that allow a diagnosis of HEC. MATERIALS AND METHODS: The sonographic and computed tomography (CT) finding s of 21 patients with proven unilocular HEC were retrospectively analysed. A total of 28 examinations were reviewed, including 14 sonograms (ultrasoun d; US) of the liver and 14 CT studies. RESULTS: Seven imaging features that help in the diagnosis of unilocular HE C were identified by US and/or CT in 14 patients (14/21; 66.6%). They are, by order of frequency: hydatid sand (29.2%), focal or segmental thickening of the cyst wall (29.2%), coexistent echinococcal cysts in the spleen or lu ngs (16.6%), pericystic biliary radicles dilatation (8.3%), atrophy of the right lobe with compensatory hypertrophy of the left hepatic lobe (8.3%), s atellite cysts typical of HEC in the liver (4.2%) and pericyst calcificatio n (4.2%). CONCLUSION: These ancillary signs should prompt us to consider HEC as the c ause of a unilocular cyst in approximately two-thirds of patients. (C) 2001 The Royal College of Radiologists.